Nobody knows how the universes biggest black holes grow so large. Now one astrophysicist says its because they feed on the quantum foam that makes up the fabric of spacetime

One of the more fascinating astrophysical discoveries in recent years is that almost all galaxies hide supermassive black holes at their cores. Indeed, astronomers believe that galaxies and black holes have a kind of symbiotic relationship so that one cannot form or grow without the other.

The evidence comes from observations of galaxies both near and faralmost all contain huge black holes.

But that raises an interesting question. We see the most distant galaxies as they were soon after the universe began. Some of these contain black holes that are a billion times more massive than the Sun but are themselves only a billion years old. The problem for astrophysicists is how these black holes could have grown so massive in such a short space of time.

Today, we get an answer from Marco Spaans at the University of Groningen in the Netherlands. He says that black holes can grow by feeding on the quantum black holes that leap in and out of existence at the smallest scale. These quantum black holes are part of the so-called quantum foam that physicists believe makes up the fabric of the Universe.

If Spaans is right, black holes grow by feeding on spacetime itself and their quantum feeding habits effectively solve the problem of how the biggest black holes become so massive, so quickly. Supermassive black holes can acquire a lot of their mass through these quantum contributions over the life time of the universe, he says.

Heres some useful background. In 1955, the American theoretical physicist John Wheeler suggested that at very small length scales, virtual particles, including quantum black holes, must constantly jump in and out of existence creating a kind of foamy structure that is very different from the smooth spacetime we see at larger scales.

Nobody has ever observed quantum foam but there is widespread agreement that the fabric of the universe must be made of something like it.

In ordinary circumstances, quantum foam has little impact. However, physicists think it must play an important role in the most extreme circumstances where the universe is being torn apart by the forces acting on it. Black holes are clearly one of these places.

Spaans approach is to ask what happens when a black hole meets quantum foam. The answer is straightforward. Quantum ﬂuctuations in the form of mini black holes can couple to macroscopic black holes and allow the latter to grow exponentially, he concludes.

He says this kind of growth can easily account for the observed size of relatively young supermassive black holes. And he goes on to predict that this mechanism could allow smaller black holes to grow too. In fact, he suggests these smaller objects, which would be difficult to observe from Earth, could make up a significant fraction of the mysterious dark matter that astronomers believe the universe must contain.

Thats interesting stuff but new ideas are worth little unless they make experimentally testable predictions and Spaans does not disappoint in this respect. He says that this quantum feeding mechanism must apply to the supermassive black hole at the centre of our galaxy and that consequently, it must be growing at the rate of about 10^-3 solar masses per year.

And that ought to be measurable. Spaans says that signals produced by pulsars are particularly sensitive to their local gravitational conditions. So it should be possible to spot the the increasing gravitational field of a growing black hole by studying pulsars that orbit close by.

He points just such a pulsar was discovered earlier this year at the centre of our galaxy and that a long-time monitoring program of its behavior is now in order.

Such a program would take years or even decades to reveal the kind of changes that Spaans predicts. But when it comes to the feeding habits of black holes, knowing whats on the menu could be priceless information.

I myself have thought about it constantly since an incredible analogy was first put out there several years ago; namely, that spacetime itself flows into black holes. And once it reaches the event horizon, it is flowing inward faster than the speed of light. That's why even light can't escape: the space in which it is embedded is flowing inward faster than c, while the best it can do is c outward. So it is carried in. Note this was only supposed to be an analogy to help you understand! Now it appears it may be something more than that.

Jeex. I bought 2 tubes of quantum foam from a bargain bin at HD 10 years ago. I put them in a storage bin. Gotta find that stuff. Any ideas what I should do if I find it? Been looking. Maybe it fell into one of those black holes that bedevil my supplies.

Wait a minute. A blended Margarita has foam! Maybe the galaxy is like a margarita. A little sweet.....a little tangy......a little salty......So that means the planets are like tortilla chips and the stars are salsa? Why, it’s a fiesta!

28
posted on 09/12/2013 7:43:35 PM PDT
by blueunicorn6
("A crack shot and a good dancer")

Well, I want to meet the black hole that can tear apart a bag of that Costco Trail Mix. I’ve pulled on those and tried to chew a little tear.....nothing. Oh, the stars may all fall away, but there will still be those little bags of Costco Trail Mix still floating around. The ones with the teeth marks will be mine.

37
posted on 09/12/2013 8:08:21 PM PDT
by blueunicorn6
("A crack shot and a good dancer")

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